1. Field of the Invention
The present invention relates to an exposure aligning method of aligning an exposure position when performing an exposure, and an exposure apparatus in which the method is realized.
2. Description of Related Art
When a pattern of an LSI circuit is formed on a semiconductor wafer, a photo-resist is used. Specifically, in forming the pattern, the photo-resist is coated on the substrate. Subsequently, light is irradiated onto the photo-resist through a reticle on which the pattern has been drawn, by an exposure apparatus. The exposure hardens or softens the photo-resist. An unnecessary portion of the photo-resist is removed after the exposure to produce the pattern. When, an etching or implantation process is performed using the produced pattern as a mask. Through this process, the pattern corresponding to one layer is formed.
In the semiconductor wafer, a plurality of patterns may be formed on a plurality of layers. In such a case, after a pattern of a first layer is formed, a film formation process of an insulating layer, a heating process, and so on is executed, and an upper layer pattern is formed by the same technique as that of the first layer. In exposing the upper layer pattern, it is necessary to adjust the relative exposure position to the lower layer pattern. In order to align the relative position of the upper layer pattern to the lower layer pattern, alignment marks are added to the lower layer pattern. When the upper layer pattern is exposed, the alignment marks in the lower layer pattern are identified and the exposure positions are determined based on the identified marks.
As a factor of a shift of the exposure position, shifts (overall shift) to an X-direction and to a Y-direction are considered when designating a substrate plane as an XY plane. The whole shifts can be corrected based on the positions of the alignment marks given to the lower layer pattern. As the factor of the shift of the exposure position, a shift of a shot component other than the whole shift can be considered. The shift of the shot component means a shift that includes a rotation of the exposure position and a telescopic shift (expansion or contraction). The shift of the shot component is produced by a manufacture error of the reticle, a mechanical error of the exposure unit, and so on.
When the exposure position is adjusted based on alignment marks, a load required to execute an aligning process at the time of exposure will increase as far as the shift of the shot component is intended to be corrected. Therefore, a correction of the shot component is omitted in some cases, when the exposure position is adjusted based on the alignment marks.
In relation to the shift of the shot component, Japanese Patent Application Publication (JP-P2000-81712A) is known, which describes an alignment correction method that includes calculating an average of actual shift amounts of a plurality of sets of products, calculating a difference of the shift amount between at least two sets of products produced consecutively, among the plurality of sets of products, and calculating an estimated stepper correction value by adding a value proportional to the shift amount of the average value.
As another technique about the shift of the shot component, Japanese Patent Application Publication (JP-A-Heisei 11-102851) is known. Japanese Patent Application Publication (JP-A-Heisei 11-102851) describes an alignment correction method in which a production system controls shift amounts from a position of reference to positions of a plurality of patterns in a semiconductor device, and the production system generates a value by adding an shift amount of its lower layer pattern corresponding to this pattern to the above-mentioned shift amount, as a stepper correction value for determining the position of the pattern.
In order to correct a shift of a shot component, it is considered to adjust an exposure position based on a pattern shift of an exposure target pattern (a shift of the exposure target pattern to the lower layer pattern) on a substrate that has been processed in past (past processed substrate), not based on alignment marks on the lower layer pattern. However, the lower layer pattern itself may have shift from the substrate having been processed in past. In this case, the shift of the lower layer pattern from the past processed substrate will be reflected to pattern shift of the exposure target pattern. Therefore, it becomes difficult to adjust the exposure position with excellent accuracy.